Tool for bending workpieces such as tubes and sections

ABSTRACT

A tool for bending workpieces such as tubes and sections, and for use in machines in which ram strokes occur in rapid succession, wherein upper and lower clamping plates having a cavity therebetween for the reception of a workpiece are superimposed and are shifted horizontally upon the reception of vertical strokes from the ram. Counter-pressure elements are disposed outwardly of the plates and inwardly of the cavity against which the workpiece bears.

United States Patent [191 Eckold et a].

1 1 TOOL FOR BENDING WORKPIECES SUCH AS TUBES AND SECTIONS [75] Inventors: Gerd-Jiirgen Eckold, St.

Andreasberg; Hans Maass, Bad Lauterberg, both of Germany [73] Assignee: Paweck AG, Chur, Switzerland [22] Filed: Sept. 9, 1974 [21] Appl. No.: 504,662

[30] Foreign Application Priority Data Sept. 7, 1973 Germany 2345138 Nov. 12, 1973 Germany 2356451 [52} US. Cl 72/389; 72/452 [51] Int. Cl. B21D 7/06 [58] Field of Search 72/315, 389, 308, 309, 72/311, 313, 452

{56] References Cited UNITED STATES PATENTS 3,256,730 6/1966 Faull .7 72/452 [451 Aug. 12, 1975 3,390,566 7/1968 Conklin 72/389 3,606,788 9/1971 Whitman v 72/389 3,686,920 8/1972 Alleaume 72/452 FOREIGN PATENTS OR APPLICATIONS 516,924 l/l953 Belgium 72/389 Primary ExaminerC. W. Lanham Assistant Examiner-M. J. Keenan Attorney, Agent, or FirmWatson, Cole, Grindle & Watson 5 7 1 ABSTRACT A tool for bending workpieces such as tubes and sections, and for use in machines in which ram strokes occur in rapid succession, wherein upper and lower clamping plates having a cavity therebetween for the reception of a workpiece are superimposed and are shifted horizontally upon the reception of vertical strokes from the ram. Counter-pressure elements are disposed outwardly of the plates and inwardly of the cavity against which the workpiece bears.

9 Claims, 20 Drawing Figures PATENTED AUG 1 2 I975 SHEET v In \w lhhhhhhhhhl! PATENTED AUG] 2 I975 SHEET 4 TOOL FOR BENDING WORKPIECES SUCH AS TUBES AND SECTIONS This invention relates to a tool for bending workpieces such as tubes and sections, and for use in machines in which the ram strokes take place in rapid succession.

In the bending of tubes and especially in the bending of sections on edge, the occurrence of folds or deformed portions in the compression zone has always caused problems and continues to do so. To avoid or eliminate these deformed portions it has been necessary to use expensive apparatus or to carry out subsequent machining operations.

The object of the present invention is to solve this problem by means of a new tool for machines in which the ram strokes occur in rapid succession. A further object is to enable a large number of workpieces such as tubes or sections to be similarly bent as in a jig in a simple and rapid manner by the use of such tools; in particular, the formation of different bends or of bends extending over varying distances is aimed at. A particular object in such operations is that of avoiding excessive bending of the workpieces that otherwise occur.

According to the invention, the tool is characterized in that a lower clamping plate and an upper clamping plate, backed by springs, are disposed one above the other for longitudinal displacement in a common holding and are so shaped on their mutually facing surfaces that together they form a cavity, corresponding to the cross-section of the particular workpiece to be bent, plus clearance in the direction of bending. Inclined faces, extending in the same direction, are formed respectively on the upper surface of the upper clamping plate and on the lower surface of a pressure plate mounted on the upper plate, the arrangement being such that each time the ram pressure is applied to the pressure plate, the clamping plates, with the workpiece clamped between them, are advanced in the direction of bending, against the resistance offered by counterpressure elements disposed at both sides, over a distance corresponding to the effective stroke of the ram. The workpiece, during its advance, is supported by its faces that trails in the direction of bending, on the wall of the clamping plate that faces it. These end walls of the clamping plates are curved. Their radius is always smaller than the required minimum radius of the workpiece.

The counter-pressure members are preferably adapted to rotate on the holder plate of the tool and match the workpiece (cross-sectional form).

In a preferred form of a tool in accordance with the invention, the end walls of the clamping plates that delimit the cavity are readily exchangeable screw-on parts.

In accordance with a further feature of the invention and particularly in the case of producing workpieces that are similarly curved as in a jig, the backing surface of the clamping plate for the workpiece extends at least as far as the effective zones of the counter-pressure members and has a curve corresponding to the radius of bend of the finished workpiece. The curve corresponding to the desired radius of bend of the finished workpiece ensures that each bent workpiece undergoes the same bending. In this way excessive bending is prevented by the counter-pressure members which act as stops, are preferably rotatable and are matched to the shape of the workpiece.

In a preferred embodiment of the invention, the backing surface for the workpiece is constituted by the front surface ofa separate shaped part, the rear surface of which bears against the associated clamping plates. Such a separate shaped part offers the advantage that the machine can be readily set up to produce workpieces of different curvature simply by changing the shaped parts. Such a shaped part may be secured to the associated clamping plate or to the workpiece itself, and in the latter case it is advanced with the workpiece in rhythm with the working cycle of the machine. The shaped part can be held on the workpiece, for example, by means of a clip or with the aid of an abutment.

The form of tool and the mode of operation described also enable workpieces with different radii of bend to be produced using the same ram setting. If, using the same ram setting, it is desired to produce workpieces having different radii of bend or lengths of bend or to obtain a workpiece which has straight or differently bent intermediate portions, the effective stroke of the ram can be adjusted to the correct value by varying the thickness of the shaped part in a different man ner.

Advantageously, the workpiece to be bent is aligned during the advance movements by fitting lateral guide arms on the clamping plates or the shaped part.

The invention will now be described in more detail with reference to the accompanying drawing, wherein:

FIG. 1 is a side elevational view of a tool in accordance with the invention;

FIG. 2 is a plan view of the tool of FIG. 1; FIG. 3 is a front elevational view of the tool of FIG.

FIG. 4 is a vertical section through a modified form of the tool;

FIGS. 5 to 8 are vertical sections through the clamping plates for various types of workpieces shown in cross-section;

FIGS. 5a to 8a show the counter-pressure members associated with the clamping plates of FIGS. 5 to 8;

FIGS. 9 to 12 illustrate modified forms of the tool of the invention; and

FIGS. to 12a are vertical sections through the modified tools of FIGS. 9 to 12.

Turning now to the drawings wherein like reference characters refer to like and corresponding parts throughout the several views, the bending machine is shown as having a ram 1 operable by conventional means (not shown) by causing it to stroke in rapid succession. The ram may comprise a resilient rubber block 2 which acts on a pressure plate 3 which, through its inclined face 3', imparts advance movements, in rhythm with the working cycle of the machine, to a pair of clamping plates 4 and 5, disposed above one another. Upper clamping plate 4 has an inclined surface 4' which slopes in the same direction as inclined surface 3 of pressure plate 3. All of the plates 3, 4 and 5 are disposed in a holder 6 and are mounted for vertical or horizontal displacement.

The upper clamping plate 4 and the lower clamping plate 5 between them form a cavity 7 which is matched to the cross-section of the workpiece to be bent which, in the example illustrated, is a box section 8 shown in plantom outline.

In the embodiment illustrated in FIGS. 1 to 3, the cavity is delimited by the downwardly extending wall 9 of clamping plate 4 and the upwardly extending wall 10 of clamping plate 5. Holder 6 comprises a holder plate 11 projecting outwardly at each of its sides, on which plate counterpressure members 12 are rotatably mounted. Also, wall 9 has an arcuate surface facing box section 8 to be bent, as shown in FIG. 2.

In the embodiment seen in FIG. 4, the end walls of the clamping plates 4 and that delimit cavity 7 are formed by wall parts 16, one of which is threaded on to the lower surface of upper clamping plate 4, and the other on to the upper surface of lower clamping plate 5.

Briefly, the mode of operation is as follows: ram 1 executes short reciprocatory movements which apply thrusts to pressure plate 3. In a first stage, depression of pressure plate 3 causes box section 8 to be clamped between the clamping plates 4 and 5, and in a second phase, clamping plates 4 and 5 are advanced in the direction of bending A, and the box section 8 clamped between the plates and bearing against end wall 9 (backing surface) is carried along by the plates which cause section 8 to be bent by reason of the resistance offered by counter-pressure member 12. In this mode of operation, a clearance 13 permitting movement is provided between the lower surface of the upper clamping plate and the upper surface of the lower clamping plate.

The two clamping plates are connected by pins and are provided with resilient rubber pads 14 or the like. Upon completion of the pressure stroke, the clamping plates spring back into their original positions. To obtain similar radii of bend, movement in the direction of bending A can be limited by a set-screw l5. The embodiment shown in FIG. 4 offers the advantage that the tool can be easily set to enable it to be used for different sections, by inserting suitable end wall parts 16.

The tool of the invention is suitable for bending the different types of section illustrated in FIGS. 5 to 8. FIG. 5 shows a tube 20, FIG. 6 a box section 21, FIG. 7 a top-hat section 22, and FIG. 8 a section 23 with a plurality of webs. The corresponding counter-pressure members 30, 31, 32 and 33 are designed to match the form of these sections.

In the embodiment shown in FIG. 9, a clamping plate 104 has lateral projections 110 so that its backing surface 109 for workpiece 108 extends as far as the effective zones of the rotatable counter-pressure members 112. This ensures uniform bending of the fitted workpieces and prevents any excessive bending. Lateral guides arms 118 on clamping plate 108, and end plates 118 ensure that the workpiece is efficiently guided (see FIG. 9a).

In the embodiment shown in FIG. 10, the curved backing surface 113 carries a separate shaped part 114 (see also FIG. 10a) which is secured to workpiece 108 by means of a clip 116. The workpiece 108 together with shaped part 114 is advanced stepwise through the tool.

A special feature of the embodiment shown in FIG. 11 is that the shaped part 114' has a abutment 117 against which the workpiece 108 bears during its advance through the tool.

In the embodiment illustrated in FIG. 12, a bend having different radii is to be imparted to a workpiece 108'. To form this bend without the need for resetting the ram, the shaped part 114" having a backing surface 113' varies in thickness as indicated at a, b and c.

Tubes or sections are generally bent by moving them manually or mechanically forward and possibly backward through the tool roughly in rhythm with the working cycle of the machine each time the ram executes an idling stroke. It may also be expedient to pull the workpiece through the tool in a stepwise manner, especially when the workpiece is to comprise straight portions.

Tubes or other hollow sections may be bent with or without a core fitted in their interior.

What is claimed is:

l. A tool for bending workpieces such as tubes and sections, and for use in machines in which the ram strokes occur in rapid succession, comprising: superimposed lower and upper clamping plates; resilient means located between said plates for maintaining them in a slight spaced-apart relationship; a holder within which said plates being disposed for horizontal shifting movement; said plates being shaped at their mutually facing surfaces to form a cavity corresponding to the crosssection of a particular workpiece to be bent; counterpressure elements on said holder spaced outwardly of said plates against which the workpiece bears; a pressure plate superimposed over said upper clamping plate for contact by the ram, the mutually facing surfaces of said upper plate and said pressure plate being correspondingly sloped in the same direction; the cavity having opposing vertical walls between which the workpiece is disposed, one of said walls in the direction of bending lying outwardly of the inner surfaces of said counter-pressure element; and the tool being such that each time the ram pressure is applied to said pressure plate, said clamping plates and the workpiece are shifted in the horizontal direction of bending opposite the corresponding slope of said upper plate and said pressure plate surfaces, the workpiece being shifted against the resistance of said counter-pressure elements over a distance corresponding to the effective stroke of the ram.

2. The tool according to claim 1, wherein the other of said walls of the cavity is convexly curved relative to said one wall.

3. The tool according to claim 1, wherein said counterpressure elements are rotatably mounted on said holder.

4. The tool according to claim 1, wherein said vertical walls are defined by elements removably secured to said clamping plates.

5. The tool according to claim 1, wherein the other of said walls of the cavity is convexly curved, and said counterpressure elements having inner surfaces forming an angle therebetween corresponding to said convexly curved other wall.

6. The tool according to claim 1, wherein a separate convexly curved element is located in said cavity against said other wall thereof, and said counterpressure elements having inner surfaces forming an angle therebetween corresponding to said convexly curved separate element.

7. The tool according to claim 6, wherein means are provided for fastening said separate element to the workpiece.

8. The tool according to claim 6, wherein means are provided on said separate element for retaining the workpiece thereon.

9. The tool according to claim 6, wherein said separate element is curved to a variable extent. 

1. A tool for bending workpieces such as tubes and sections, and for use in machines in which the ram strokes occur in rapid succession, comprising: superimposed lower and upper clamping plates; resilient means located between said plates for maintaining them in a slight spaced-apart relationship; a holder within which said plates being disposed for horizontal shifting movement; said plates being shaped at theIr mutually facing surfaces to form a cavity corresponding to the cross-section of a particular workpiece to be bent; counter-pressure elements on said holder spaced outwardly of said plates against which the workpiece bears; a pressure plate superimposed over said upper clamping plate for contact by the ram, the mutually facing surfaces of said upper plate and said pressure plate being correspondingly sloped in the same direction; the cavity having opposing vertical walls between which the workpiece is disposed, one of said walls in the direction of bending lying outwardly of the inner surfaces of said counter-pressure element; and the tool being such that each time the ram pressure is applied to said pressure plate, said clamping plates and the workpiece are shifted in the horizontal direction of bending opposite the corresponding slope of said upper plate and said pressure plate surfaces, the workpiece being shifted against the resistance of said counter-pressure elements over a distance corresponding to the effective stroke of the ram.
 2. The tool according to claim 1, wherein the other of said walls of the cavity is convexly curved relative to said one wall.
 3. The tool according to claim 1, wherein said counterpressure elements are rotatably mounted on said holder.
 4. The tool according to claim 1, wherein said vertical walls are defined by elements removably secured to said clamping plates.
 5. The tool according to claim 1, wherein the other of said walls of the cavity is convexly curved, and said counterpressure elements having inner surfaces forming an angle therebetween corresponding to said convexly curved other wall.
 6. The tool according to claim 1, wherein a separate convexly curved element is located in said cavity against said other wall thereof, and said counter-pressure elements having inner surfaces forming an angle therebetween corresponding to said convexly curved separate element.
 7. The tool according to claim 6, wherein means are provided for fastening said separate element to the workpiece.
 8. The tool according to claim 6, wherein means are provided on said separate element for retaining the workpiece thereon.
 9. The tool according to claim 6, wherein said separate element is curved to a variable extent. 